Surface veil of oxidized PAN fiber

ABSTRACT

A nonwoven veil comprising an oxidized PAN fiber having an aromaticity index between 40 and 60 percent, wherein the veil is thermally stable in temperature ranges used for typical composite fabrication processes. Thermally stable nonwoven veil and composites containing the veil are disclosed. The nonwoven veil could be used as a surface finish having improved properties as measured by surface waviness and lack of defects.

FIELD OF INVENTION

The present invention relates to a carbonaceous fiber nonwoven veil, preferably of oxidized polyacrylonitrile (PAN) fiber, for fiber reinforced plastic composites to substantially eliminate surface waviness of the composites incorporating the veil and thereby improve finish cosmetics of the composites.

BACKGROUND

A composite material is a material system composed of two or more constituents differing in form and/or material composition, and that preferably are essentially insoluble in each other. Major constituent forms used in composite materials are fibers, particles, laminae or layers, flakes, fillers and matrices. Fiber reinforced plastic materials provide mechanical performance and fabrication characteristics which make these composites the preferred material of choice for a large number of applications.

Fiber reinforced composites are generally made by molding high modulus reinforcing fibers with a resin matrix. The molding or fabrication process is a complex process. What makes the fabrication of these materials so complex is that it involves simultaneous heat, mass, and momentum transfer, along with chemical reactions in a multiphase system with time-dependent material properties and boundary conditions. Composite manufacturing requires knowledge of chemistry, polymer and material science, rheology, kinetics, transport phenomena, mechanics, and control systems. Therefore, at first, composite manufacturing was somewhat of a mystery because of the very diverse knowledge that was required of its practitioners. Even now, people do not fully understand the different fundamental aspects of composite processing. During the molding process the fiber and resin may respond differently to environmental conditions such as temperature and pressure. These differences can diminish the quality of surface finish that may result. Commercial success of composite products often requires substantial post-molding finish work to repair or cover cosmetic blemishes. A large body of work has been dedicated toward improving the surface finish quality of molded composite products.

When thermosetting polymers are used, shrinkage is typically observed as the polymer catalyzes. Selection of polymers and inclusion of shrinkage control additives may be largely influenced by the required cosmetics of the finished part. Thermoplastic polymers shrink according to their thermal expansion response over the temperature differential required for molding, from an elevated temperature required to flow, back down to a temperature to congeal, and finally down to a normal use temperature. The reinforcement fibers intended to provide the rigidity and strength of the composite material typically resist the global shrinkage of the resin matrix. However, since reinforcement fibers have a substantially cylindrical shape, it is evident that the ability to control shrinkage can not be perfectly uniform when examined at the dimensions of the fibers themselves. Groups of fibers in a substantially aligned orientation can result in aligned waves of a composite part surface, which may be easily observed by variation of reflected light. Random fiber orientations may also create a “matt” finish rather than “glossy”, due to the imperfections of fiber dispersion.

The optical appearance of the molded product may be so affected that the fiber orientations within the outer layers of the composite become discemable. This phenomenon is often referred to as “print” or “print-through”, or “read-through” among other terms. For those skilled in the art, it may be possible to distinguish from a molded part what type of reinforcements have been used, such as chopped or continuous strand mat, woven, or warp-knitted non-crimp fabric, etc. In some instances, material defects may be observed including missing ends from fabrics, creases and wrinkles, or gaps between reinforcement fabrics.

U.S. Pat. No. 4,435,349 describes the use of a surface veil to limit the visibility of glass strands on the surface of a molded composite part. U.S. Pat. No. 5,391,344 discloses surface veils of filamentized polyester or glass to produce a smooth surface on a reinforced plastic laminate. Furthermore, this patent describes a means of measuring surface quality according to “Distinctness Of Image” by using a “Digital DOI Goniphotometer.” Examples were provided to show a relationship between DOI measurements and the amount of surface veil used when molding composite parts of Glass Fibers and Polyurethane Resin by the process of Reaction Injection Molding (RIM). Examples were shown of evaluated glass fiber (17 micron) veils of varying area weights from 34 gsm to 136 gsm, and it was determined that the best surface finish was achieved when a minimum of 100 gsm was used, for panels produced with a total weight percent of glass between 19.9 and 30.4 percent.

U.S. Pat. No. 5,391,344 discloses surface veils that are generally highly filamentized, and references two manufacturers of surface veils. Each of these manufacturers, either by product literature or patents have cited a method used for creating veils of glass fiber described in U.S. Pat. No. 2,574,221 and 2,081,060. This method produces a helically wound strata of substantially parallel fibers or of intercrossed fibers, which are then stretched so that the thickness is reduced and the entire body becomes highly porous having a large proportion of voids therein and so that the number of crossing points between individual threads is more or less rarified. Although less dense than dense reinforcement products, the surface veils of this process still result in discernable surface defects in composite products.

Despite the prior art uses of surface veils, particularly glass fiber veils in RIM processes, there is substantially no disclosure of oxidized PAN fiber nonwoven veils to provide a low coefficient of thermal expansion and to minimize shrinkage and cosmetic defects associated with molding fiber reinforced plastic composites. In short, the prior art surface veil products form poor and random quality of surface finish that cannot be explicitly defined and there is a need for a high quality nonwoven veil of oxidized PAN fiber.

SUMMARY OF THE INVENTION

This invention relates to a nonwoven veil of oxidized PAN fiber to control shrinkage for improved finish cosmetics of fiber reinforced plastic composites. The veils could be made by various textile processes including hydro-entanglement to create a material which may be molded with either thermosetting or thermoplastic resins to achieve a substantially uniform and quasi-isotropic fiber structure in the resins.

One embodiment of this invention is a nonwoven veil comprising an oxidized PAN fiber having an aromaticity index between 40 and 60 percent, wherein the oxidized PAN fiber exhibits thermal stability from room temperature to 260° C. such that the oxidized PAN fiber has substantially negligible shrinkage up to 260° C. Preferably, the veil has a substantially uniform and quasi-isotropic fiber structure. Preferably, a content of the oxidized PAN fiber is between 85 and 100 percent by weight of the veil. In one variation, a content of a secondary fiber is between 0 and 15 percent by weight of the veil. Preferably, the secondary fiber is between 0 and 15 percent by weight of a thermofusible fiber or a bi-component thermofusible binder. Preferably, the area weight of the veil is between 35 and 120 grams per square meter. Preferably, the oxidized PAN fiber has a linear density between 1.2 and 6.0 dtex. More preferably, the oxidized PAN fiber has a linear density between 1.5 and 2.4 dtex. Preferably, the oxidized PAN fiber is a crimped staple fiber. Preferably, the veil is made by a textile process selected from the group consisting of hydro-entanglement and needle-punching. Preferably, the oxidized PAN fiber is substantially non-thermoplastic. Preferably, the oxidized PAN fiber has shrinkage in the range of about 0-13 percent at an elevated temperature between 260° C. and 730° C. More preferably, the oxidized PAN fiber has a shrinkage of about zero percent at a temperature between room temperature to about 260° C.

Another embodiment is a fiber reinforced plastic composite material comprising the veil of this invention and a thermosetting resin and/or a thermoplastic resin. Preferably, the veil of is preformed using an elevated temperature that activates a thermofusible component. Preferably, the veil is thermally bonded to a reinforcement material. More preferably, the veil is stitch bonded to a reinforcement material. In one variation, the veil is combined with a reinforcement material and a resin. In another variation, the composite material is made by a molding process comprising a step at an elevated temperature above the room temperature. Preferably, the composite has substantially no global distortion. Preferably, the veil does not substantially print-through the composite material.

Additional advantages of this invention could become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiments of this invention are shown and described, simply by way of illustration of the best mode contemplated for carrying out this invention. As will be realized, this invention embraces other and different embodiments, and its details are capable of modifications in various obvious respects, all without departing from this invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.

DETAILED DESCRIPTION

This invention relates to the incorporation and use of oxidized PAN fibers for the production of a nonwoven veil according to various textile processes including hydro-entanglement to create a material which may be molded with either thermosetting or thermoplastic resins to achieve a substantially uniform and quasi-isotropic fiber structure, providing a low coefficient of thermal expansion to minimize shrinkage and cosmetic defects associated with molding fiber reinforced plastic composites.

Surface veils of this invention may also be used to provide a particular environmental barrier for composite products, including corrosion resistance and UV resistance. This includes veils of different combinations of PAN fibers and other fibers such as glass fibers of chemistries A, C, and E, and synthetic polymer fibers of polyester, Nylon and fluoropolymer. The processes for forming the veils of this invention may include continuous strand, chopped strand, wet-lay up, spun-bond, spun-lace, hydro-entanglement, etc. Veils could also be adapted according to various composite fabrication processes including winding, pultrusion, and resin transfer techniques ranging from vacuum infusion to pressure injection, as well as lamination with thermoplastics.

Surface veils are typically light weight nonwoven fabrics placed on the outermost layers of a reinforced plastic laminate. In the most general sense, the surface veils of this invention are intended to support a layer of resin at the surface of a composite part, which provides characteristics that are distinguished from the bulk of the structurally reinforced composite. This is often described as a “resin rich” layer such that the structural composite has a higher fiber volume fraction.

By placing all materials in a closed mold of a given cross section thickness, both surface veils and structural fiber products would occupy similar fiber volumes if their fiber geometry were the same. In order for surface veils to define a layer that is relatively “resin rich,” a few specifics were recognized by the inventors of this invention. First, the surface veils should preferably possess a fiber geometry that is less dense than that of the reinforcement layers. Second, substantially aligned fibers could occupy the least volume by “packing,” and therefore the unidirectional fibers of pultrusion or tape based prepreg can achieve fiber volumes in excess of 65 percent. Non-crimp fabrics may be produced which exceed 60 percent and woven fabrics may be greater than 55 percent. Randomly oriented mats for structural reinforcements typically define a much lower fiber volume than aligned fiber structures, and the prospective range may also be quite large.

In one embodiment, the surface veil could be a mat. Mats could be a non-woven material, composed of uniformly distributed fibers, which are bound by means of organic additives, mainly thermosetting resins. In the case of a random fiber mat used within a given cross section, it was found that they should preferably “loft” in order to adequately distribute the reinforcement fibers across the total thickness. This is the case for mats typically developed as continuous strands with a swirled and looping geometry that creates loft and “spring-back.”

Fiber volume percent is defined as the percentage of volume occupied by fiber in a composite. It is typically calculated by the following formula: Fiber volume percent=[(W/F)/(w/c)]×100 wherein:

-   W=weight of the fiber in the composite, -   w=weight of the initial composite specimen, -   F=fiber density, and -   c=composite density

In a mat having multiple filaments maintained in bundles or strands, the strands of aligned fibers may possess from 50 to 200 individual filaments. According to these variables in fiber geometry, randomly oriented mats for structural composites may provide fiber volumes over a wide range from 10 to 45 percent.

In order for surface veils to support a relatively resin rich layer, preferably the fiber structure should define a very low fiber volume percent. The inventors of this invention recognized that the construction with fiber as strata permits the possibility of a fiber remaining in contact with the mold surface over a significant length, and the creation of porosity (which is a problem) by a rarified distance between crossing points defines a repetitive grid like structure with relatively large areas of un-reinforced resin.

It was also recognized that the density of the filaments could also influence the amount of fiber by weight necessary to define a given volume, and therefore the thickness of the resulting veil. For example, with a surface veil of a polyester fiber having a density of approximately half that of glass, the same quality of surface could be achieved with a polyester veil of half the area weight as for the glass veil. Quality of surface is described by waviness, by reflective light, and other surface defects, such as fish eyes, brightness or dullness, print-through, etc.

It was also recognized that the filament diameter of the fibers of a surface veil could also influence the quality of the surface finish produced by the surface veil. For example, a typical glass fiber has a 17 microns nominal diameter. The production rate of glass fibers is directly influenced by their diameter, and smaller fibers are increasingly difficult to produce efficiently, so that the cost of producing glass veils could be optimized in this range. Whereas, the production of synthetic fibers is not based upon the same parameters as glass, so that smaller diameter filaments could still be economical to produce. This, in combination with lower material densities, could permit synthetic fibers to establish a very fine fiber network, of low fiber volume, and of low area weight compared with that of glass fiber.

Random orientations of individual filaments can occupy a significant volume with a minimal amount of fiber, particularly if the random orientations are throughout the thickness, rather than super-positioned strata. Synthetic fibers also retain the possibility to have “crimp.” This crimping process provides filaments with a geometry that could avoid packing of filaments, further define loft of a batt of crimped fiber, and increase mechanical strength of a web when the fibers are entangled. The process of crimping is not practical for a mineral fiber such as glass, but possible in a synthetic thermoplastic or elastomeric fiber. This combination of features could permit randomly oriented synthetic fiber veils to exhibit a very “soft touch” particularly when compared with the abrasive feel of a mineral fiber veil. For the composite material, this may also demonstrate benefits in surface appearance since an individual filament is less likely to be pressed to the mold surface along its length, or to have a relatively sharp and stiff filament end exposed at the surface.

Despite the numerous prospective advantages of synthetic fibers versus glass for use in surface veils, the applicants recognized that one disadvantage remains due to the very nature of synthetic fiber being thermoplastic or elastomeric. Mineral fibers such as glass are considered thermally stable, and are substantially insensitive to the temperature ranges associated with composite product manufacturing and use. On the other hand, the synthetic polymers of polyester, Nylon, and PAN commonly used for surface veils exhibit limitations in use due to their thermal response.

A variety of acrylic fibers containing a minimum of 85 percent acrylonitrile and a maximum of 15 percent co-monomers can be used as PAN precursor fiber for the production of oxidized PAN fiber. But the PAN precursor fiber will more preferably contain no more than 8 percent co-monomer such as methyl-methacrylate, methyl acrylate, itaconic acid, vinyl acetate, vinyl chloride, and other monovinyl compounds. Thermal stabilization of PAN precursor fiber is carried out in an oxidizing atmosphere such as air, in a temperature range between 180° C. and 300° C. Heating rate can vary depending on the PAN precursor fiber chemistry. The process is typically performed on continuous fiber tow containing 3,000 to 400,000 filaments held under controlled tension. The process can yield a substantially non-thermoplastic black fiber, which is thermally stable.

The degree of thermal stabilization for oxidized PAN fiber can be characterized by its aromatic index. The aromaticity preferred for use in this invention can range between 40 percent and 60 percent and can vary depending on the decitex of the oxidized PAN fiber being used. Another indicator of aromaticity, which can be used for in-process inspection, is fiber density. FIG. 1 shows the correlation between aromaticity and fiber density for several samples (A1 to B4) of the oxidized PAN fiber. Fiber densities from 1.35 g/cc to 1.4 g/cc (depending on decitex) can provide a general indication that the desired range of aromaticity has been achieved, and the stabilization process is functioning properly.

The PAN precursor fibers may be oxidized to achieve good thermal properties, and yet still retain much of their textile capabilities such as crimping the fibers. These fibers are well suited to further textile processes including carding, needle-punching, air-laying, and hydro-entangling, among others. A typical felting process including needle-punching may be used to produce a veil of oxidized PAN fibers. In a preferred embodiment of this invention, the use of hydro-entanglement is used such that the water-jets do not impart a residual pattern, and the fiber entanglement is sufficiently high to provide mechanical stability to a low area weight veil below 100 gsm.

In an embodiment of the surface veil of this invention, a chemical binder could be used to maintain the integrity of the veil, including a paper-making type of process. A bindered veil could be relatively stiff and inelastic, which is frequently desired in molded composite products. Alternatively, in another embodiment of this invention, a secondary fiber type may be distributed throughout the veil and used as a thermoplastic adhesive. This could either be a fiber with a relatively low temperature melting point, or a bi-component fiber that uses a low melt temperature exterior about a high temperature core. Incorporating these secondary fibers can provide the veil with additional features useful in the course of the assembly, transport, and shape stability of the reinforcement fiber materials during the composite fabrication processes.

In another embodiment of the invention, the high temperature resistance of the oxidized PAN veil allows a process of thermally laminating a reinforcement layer directly to the veil to provide intermediate products for subsequent composite fabrication. In one example, the veil is laminated to unidirectional oriented carbon fibers, using a thermally activated adhesive web to join them together. In this case, the veil could support the temperatures required for thermal lamination process without shrinkage or fusion of the fibers within the veil, and become the support for the unidirectional fibers, which heretofore had no dry mechanical integrity. In a similar example, the veil is laminated to a reinforcement fabric, either woven or non-crimp. The examples are provided without limitation to the types of reinforcement materials, which may be laminated to the veil.

In another embodiment of the invention, the high temperature resistance of the oxidized PAN veil allows a process of thermally forming the veil along with the reinforcement materials, often referred to as “pre-forming” without deleterious consequences typically observed with other synthetic fiber veils. In this case either the veil alone, or as a laminated intermediate product as described above, may be combined with reinforcement materials and subjected to high temperatures including actinic sources such as infra-red lamps. As typically practiced, the process of thermal preforming involves heating the fiber reinforcements until thermally sensitive binders incorporated therein are softened, then forming the reinforcements to a shape approximating the article to be molded by some method of pressure or vacuum, and then permitting the shaped reinforcement to cool until the binders stabilize and provide shape retention of the “preform.” The oxidized PAN veil may be used through this process without substantial risk of shrinkage, or safety hazards including emission of noxious fumes or ignition.

The oxidized PAN veil is also well suited for other processes of high temperatures including compression molding, pultrusion, reaction injection molding, resin transfer molding, autoclaving, thermoplastic lamination, or any other process that requires elevated temperatures. This consideration may not be solely based upon the ability of the veil to adequately resist the process temperatures, but may also be based upon thermal stability of the molded composite products, and any changes which may occur as the product is cooled from the molding temperature down to a normal use temperature.

In one embodiment of this invention, the oxidized PAN veil could be used in lieu of a polymer veil, for example, a polyester veil, to decrease the global distortion in shape of a composite during curing. Thermal shrinkage of a synthetic thermoplastic or elastomeric veil encapsulated within a lower shrinkage resin system can cause a global distortion in shape, or local defects including voids and surface blemishes. At an elevated temperature for molding, a fiber such as polyester would expand from its room temperature diameter and displace a resin matrix as it is react prior to gelling and solidification. Upon cooling, the polyester fiber could shrink and return to its original diameter, while the thermosetting resin may more closely retain the larger dimension as molded. The result is the creation of a void about the polyester fiber. Since thermal cycle also affects the length of the fiber, the contraction during cooling can develop an internal stress within the composite resulting in a change of shape. Often a shaped part may have a relatively imperceptible difference in curvature, and the greatest difficulty may be to keep flat panels flat. Any variations in the quality of the veils may also become evident as part-to-part dimensional changes. These issues are significantly alleviated for oxidized PAN veil, compared with other synthetic fiber-based veils.

EXAMPLES

Example veils were produced using for oxidized PAN staple fiber of Pyron®—a registered trademark of Zoltek Corporation. In the making of the veil, the process of this invention begins with oxidized PAN fibers which have been crimped and stapled (cut to about 60 mm lengths). This material is fuzzy looking with lots of individual fibers and fiber bundles arranged essentially randomly in a plane with some third dimensional spirals of fibers. This material is then carded into a flat, non-woven fabric and stabilized with a water jet perpendicular to the plane of the fabric. The U.S. patent covering this water jet process for non-wovens is U.S. Pat. No. 5,279,878—Flame Barrier Made of Nonwoven Fabric, filed Jan. 18, 1994, by Freudenberg, incorporated herein by reference. One aspect of the surface veil of this invention is that a substantial amount of the oxidized PAN fibers are oriented out of the plane of the veil. For example, the veil could have at least about 20 percent, more preferably about 35 percent, of the oxidized PAN fibers oriented out of the plane of the veil. EXAMPLE I Data Sheet: Jettex IG 65 Date: 23/05/03 Test Test Method Unit Value Area Weight ISO 9073.1 gsm 69 Thickness ISO 9073.2 mm 1.0 Bulk g/dm³ 69 Density L (MD) T (CD) Tensile Strength ISO 9073.3 daN 3 3.9 Elongation ISO 9073.3 percent 51 50 Tear Strength DIN daN 0.5 0.5 53356 Fiber Density g/cm³ 1.35 Filament Tex dtex 2.2 Fiber Volume % 5.1

EXAMPLE II Data Sheet: IK-FCFELT- 001 Date: 25.06.00 Test Test Method Unit Value Area Weight ASTM 3776-37 gsm 110 Thickness ASTM 5729-95 mm 0.6 Bulk g/dm³ 183 Density L (MD) T (CD) Tensile Strength ASTM D5035 N 44.9 25.0 Elongation ASTM D5035 percent 40.9 117.2 Tear Strength ASTM D1117 N 24.0 16.1 Fiber Density g/cm³ 1.35 Filament Tex dtex 2.2 Fiber Volume % 13.7

For the examples provided, the ISO standard and the ASTM standard are virtually identical tests. The units used to describe the sample dimensions, the test rates, and the measured values are either in metric or English terms accordingly. The results may be converted to similar units, and directly compared. Area weight is a measure of the mass for a unit area. The actual test area is a circle of 100 square centimeters (11.2 cm diameter). Thickness is measured with a caliper incorporating a pressure plate of a specific diameter, and loaded with a weight, to provide a specific pressure. Bulk density (of the material) is calculated by the division of Area Weight by Thickness (checking that units are appropriate). Tensile Strength is a measure of Tensile Load Capacity for a unit width of material, and is typically reported for both the Machine Direction Longitudinal axis, and the Cross Machine Direction Transverse axis. Elongation is the percentage of length increase when subjected to the Tensile Load Capacity. Tear Strength measures the resistance to terminal failure after a flaw is introduced. Fiber Density is the unit mass density of the fiber. Filament tex is a linear mass density of an individual filament. The term “dtex” is a measure of grams per 10,000 meters of an individual filament. Fiber volume fraction (percent) is a calculation based upon the composite material volumetric density and the fiber density and the corresponding weights of composite material and fiber.

The above description is presented to enable a person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the preferred embodiments could be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Thus, this invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. Finally, the entire disclosure of the patents and publications referred in this application are hereby incorporated herein by reference. 

1. A nonwoven veil comprising an oxidized PAN fiber having an aromaticity index between 40 and 60 percent, wherein the oxidized PAN fiber exhibits thermal stability from room temperature to 260° C. such that the oxidized PAN fiber has substantially negligible shrinkage up to 260° C.
 2. The veil of claim 1, wherein the veil has a substantially uniform and quasi-isotropic fiber structure.
 3. The veil of claim 1, wherein a content of the oxidized PAN fiber is between 85 and 100 percent by weight of the veil.
 4. The veil of claim 1, wherein a content of a secondary fiber is between 0 and 15 percent by weight of the veil.
 5. The veil of claim 4, wherein the secondary fiber is a thermofusible fiber.
 6. The veil of claim 4, wherein the secondary fiber is a bi-component thermofusible binder.
 7. The veil of claim 6, wherein a content of thermofusible binder is between 0 and 15 percent by weight.
 8. The veil of claim 1, wherein an area weight of the veil is between 35 and 120 grams per square meter.
 9. The veil of claim 1, wherein the oxidized PAN fiber has a linear density between 1.2 and 6.0 dtex.
 10. The veil of claim 1, wherein the oxidized PAN fiber has a linear density between 1.5 and 2.4 dtex.
 11. The veil of claim 1, wherein the oxidized PAN fiber is a crimped staple fiber.
 12. The veil of claim 1, wherein the veil is made by a textile process selected from the group consisting of hydro-entanglement and needle-punching.
 13. The veil of claim 1, wherein the oxidized PAN fiber is substantially non-thermoplastic.
 14. The veil of claim 1, wherein the oxidized PAN fiber has shrinkage in the range of about 0-13 percent at an elevated temperature between 260° C. and 730° C.
 15. The veil of claim 1, wherein the oxidized PAN fiber has shrinkage of about zero percent at a temperature between room temperature to about 260° C.
 16. A fiber reinforced plastic composite material comprising the veil of claim
 1. 17. The fiber reinforced plastic composite material of claim 16 comprising a thermosetting resin.
 18. The fiber reinforced plastic composite material of claim 16 comprising a thermoplastic resin.
 19. The fiber reinforced plastic composite material of claim 16, wherein the veil of is preformed using an elevated temperature that activates a thermofusible component.
 20. The fiber reinforced plastic composite material of claim 16, wherein the veil is thermally bonded to a reinforcement material.
 21. The fiber reinforced plastic composite material of claim 16, wherein the veil is stitch bonded to a reinforcement material.
 22. The fiber reinforced plastic composite material of claim 16, wherein the veil is combined with a reinforcement material and a resin.
 23. The fiber reinforced plastic composite material of claim 16, wherein the composite material is made by a molding process comprising a step at an elevated temperature above the room temperature.
 24. The fiber reinforced plastic composite material of claim 16, wherein the composite has substantially no global distortion.
 25. The fiber reinforced plastic composite material of claim 16, wherein the veil does not substantially print-through the composite material. 